Diffuser vane for a compressor device and diffuser assembly comprised thereof

ABSTRACT

Embodiments of a diffuser vane comprise a vane body with a leading edge and a trialing edge that can rotate about the leading edge to improve performance of a compressor device. This configuration maintains the position of the leading edge on the diffuser vane relative to the orientation of the working fluid. In one embodiment, the diffuser vane incorporates a support element that couples with the vane body. The support element counteracts stimulating frequencies to reduce vibration of the vane body. The diffuser vane can also comprise an armature, which couples with a force coupler to facilitate rotation of the trailing edge when in position in a compressor device.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to compressor devices (e.g., centrifugal compressors) and, in particular, to diffusers and diffuser vanes for a compressor device.

Compressor devices (e.g., centrifugal compressors) use a diffuser assembly to convert kinetic energy of a working fluid into static pressure by slowing the velocity of the working fluid through an expanding volume region. An example of the diffuser assembly utilizes several diffuser vanes in circumferential arrangement about an impeller. The design (e.g., shapes and sizes) of the diffuser vanes, in combination with the orientation of the leading edge and the trailing edge of the diffuser vanes with respect to the flow of the working fluid, often determine how the diffuser vanes affix within the diffuser assembly.

To add further improvement and flexibility to the design, some examples of the diffuser assembly incorporate variable diffuser vanes. These types of diffuser vanes can move to change the orientation of the leading edge and the trailing edge. This feature helps to tune operation of the compressor device. Known designs for variable diffuser vanes rotate about an axis that resides in the lower half of the diffuser vanes, i.e., closer to the leading edge than the trailing edge.

The location of the axis of rotation permits the trailing edge to sweep through large angles and, thus, enables better tuning and optimizing of the performance of the compressor device. However, although use of these variable diffuser vanes can improve performance, implementation of the conventional designs for variable diffuser vanes move (e.g., rotate) both the trailing edge and the leading edge with respect to the incoming working fluid. The change in position of the leading edge can cause the flow of the working fluid to prematurely separate from the surface of the diffuser vane, which can reduce the effectiveness of the variable diffuser vane to tune performance of the compressor device.

BRIEF DESCRIPTION OF THE INVENTION

This disclosure presents embodiments of a diffuser vane with a structure that permits the leading edge to rotate about the trailing edge, maintains the orientation of the leading edge relative to the direction of flow of the working fluid, and prevents unwanted vibration in response to stimulating frequencies that can occur during operation of the compressor device. These features help to maintain the structural integrity of the diffuser vane, which can lead to component failure due to cyclic fatigue. The embodiments below, for example, embody constructions that tune the diffuser vane to modes of excitation. The resulting structure has mechanical properties (e.g., stiffness) that avoid frequency modes that are stimulated, e.g., by blade pass frequency, while promoting much lower stress values. In one embodiment, the structure utilizes a vane body (e.g., an airfoil) and a base structure that provides both vibration and structural support. In one example, the base structure has sufficient lateral width and longitudinal length, with respect to the vane body, to avert potential vibration that result from modal frequencies. This same base structure also allows the orientation of the diffuser vane to change, e.g., to rotate to improve performance of the compressor device.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made briefly to the accompanying drawings, in which:

FIG. 1 depicts a schematic diagram of an exemplary embodiment of a diffuser vane;

FIG. 2 depicts a perspective view of an exemplary embodiment of a diffuser vane;

FIG. 3 depicts a side view of the diffuser vane of FIG. 2;

FIG. 4 depicts a top view of the diffuser vane of FIG. 2;

FIG. 5 depicts a back, perspective view of an example of a diffuser assembly that incorporates an exemplary embodiment of a diffuser vane, e.g., the diffuser vanes of FIGS. 1, 2, 3, and 4;

FIG. 6 depicts a front, perspective view of the diffuser assembly of FIG. 5;

FIG. 7 depicts the diffuser assembly of FIGS. 5 and 6 in exploded form;

FIG. 8 depicts a back, perspective view of an example of a compressor device that incorporates an exemplary diffuser assembly, e.g., the diffuser assembly of FIGS. 5, 6, and 7;

FIG. 9 depicts a front view of the compressor device of FIG. 8; and

FIG. 10 depicts a front, perspective view of the compressor device of FIGS. 8 and 9.

Where applicable like reference characters designate identical or corresponding components and units throughout the several views, which are not to scale unless otherwise indicated.

DETAILED DESCRIPTION OF THE INVENTION

The discussion below focuses on construction and implementation of diffuser vanes to realize better performance for compressor devices, e.g., centrifugal compressors. In one aspect, designs for the diffuser vanes allow the trailing edge to rotate to various angular positions while maintaining the orientation of the leading edge relative to the direction of flow of a working fluid that flows past the diffuser vane to prevent flow separation. These designs also stabilize the diffuser vane to prevent vibrations of the diffuser vanes in response to stimulating frequencies that can damage to the diffuser vane.

These diffuser vanes find use in a diffuser assembly, the operation of which can tune the performance of compressor devices. The diffuser assembly can incorporate a plurality of the diffuser vanes. In one example, the diffuser assembly ties the diffuser vanes to a common actuator to facilitate adjustment of the position of the trailing edge, e.g., in response to changes in the direction of the flow of the working fluid.

FIG. 1 depicts a schematic representation of an exemplary embodiment of a diffuser vane 100 to provide an overview of aspects of the proposed designs. The diffuser vane 100 includes a vane body 102, a support element 104, and an armature 106. The vane body 102 has a top 108, a bottom 110, a leading edge 112, and a trailing edge 114. The vane body 102 also has a rotation axis 116 that permits the diffuser vane 100 to move (e.g., rotate) to change the orientation of the trailing edge 114, e.g., between a plurality of angular positions.

The vane body 102 embodies an aerodynamicallyshaped element (e.g., an airfoil) that comes in contact with a flow F of a working fluid, e.g., in a centrifugal compressor. This part of the diffuser vane 100 is subject to significant loading that results from the velocity of the flow F. These loads can vibrate the vane body 102. The resulting vibrations can excite the vane body 102 at frequencies that can cause structural damage to the diffuser vane 100, which can interfere with the flow of working fluid across the surfaces of the vane body 102. For example, damage to the vane body 102 can change the orientation of the vane body 102 with respect to the flow F, which can cause the flow F to separate from surfaces of the vane body 102. Flow separation changes the fluid dynamics of the flow F. These changes, in turn, can negatively impact the overall performance and efficiency, e.g., of the centrifugal compressor.

To this end, the support element 104 provides sufficient support to the vane body 102 to damp potential vibrations that might occur in the vane body 102. Examples of the support element 104 also allow the vane body 102 to rotate about the rotation axis 116. However, configurations of the support element 104 do not interfere with the flow F at or near the surface of the vane body 102. In one example, the support element 104 fits into a feature (e.g., bore) so as to recess the support element 104 out of the flow of the working fluid. Consequently, this feature maintains the aerodynamics of the vane body 102 as well as addresses structural vibration and stress design constraints.

The armature 106 facilitates movement (e.g., rotation) of the vane body 102. At a high level, examples of the armature 106 can comprise one or more structural elements that, alone or in combination, can transfer a force to the vane body 102. This force, in one example, rotates the vane body 102 to position the trailing edge 114 in alignment and/or in optimal orientation relative to the direction of the flow F. The structural elements can transfer the force directly, e.g., as a shaft coupled with the support element 104 and/or the vane body 102. In other example, the structural elements can include various elements and devices (e.g., gears, pulleys, linkages, etc.) that couple force indirectly to move the vane body 102 as set forth herein.

As shown in FIG. 1, the armature 106 has a structure that secures to the support element 104 on one end. The structure is resilient to loading, e.g., at and/or near the end opposite the support element 104. In one example, the structure has an axis that aligns with the rotation axis 116. However, this disclosure contemplates that the armature 106 can still impart movement to the vane body 102 in an offset or relatively misaligned orientation with the rotation axis 116 and/or other parts and structure that make up the diffuser vane 100.

Collectively, the elements (e.g., the vane body 102, the support element 104, and the armature 106) can form a monolithic or cohesive unit, e.g., a unitary structural element that includes the support element 104 and the armature 106. Such a design may comport with manufacturing techniques (e.g., milling, machining, casting, molding, etc.) that afford extensive production of a plurality of the diffuser vanes 100. On the other hand, the present disclosure also contemplates configurations of the diffuser vane 100 in which construction embodies a number of pieces and piece parts. These multipiece designs can utilize any variety of types and styles of fasteners (e.g., screw, bolts, etc.) and fastening techniques (e.g., adhesives, welds, etc.) to secure the parts together to withstand subject loading and other parameters in which the diffuser vanes 100 are deployed.

FIGS. 2, 3, and 4 depict another exemplary embodiment of a diffuser vane 200. FIG. 2 illustrates a perspective view of the diffuser vane 200. The illustrations of FIGS. 3 and 4 show the diffuser vane 200 in, respectively, a top view and a side view. Together, the diagrams of FIGS. 2, 3, and 4 illustrate exemplary structure for the vane body 202, the support element 204, and the armature 206. This structure provides necessary strength to avoid the onset of vibration in the vane body 202 and also facilitates rotation of the vane body 202 about the leading edge 212. Moreover, the structure does not diminish the aerodynamics of the vane body 202, thereby maintaining proper flow F of the working fluid as the flow F passes across the surfaces of the vane body 202. While specific structure is shown, this disclosure contemplates variations (e.g., changes in shape, size, dimensions, etc.) that would perform the same and/or similar functions.

In FIG. 2, the exemplary structure of the support element 204 forms a boss 218 with a stepped profile. The armature 206 includes a cylindrical body 220 with a central axis 222 that is coaxial with the rotation axis 216. The cylindrical body 220 has a plurality of sections (e.g., a top section 224, a middle section 226, and a bottom section 228), which vary in dimensions (e.g., diameter). The top section 224 forms a round disc 230 with a disc surface 232 on which the support element 204 is disposed. In one example, the round disc 230 resides in a feature of a diffuser assembly to recess the round disc 230 out of the flow of the working fluid. The middle section 226 forms a cylindrical sleeve 234 with a diameter that is smaller than the diameter of the round disc 230. The cylindrical sleeve 234 can act as a bearing surface to support the diffuser vane 200 and corresponding structure. In the bottom section 228, the cylindrical body 220 forms a shaft 236 that, as discussed more below, couples with a force coupler, e.g., to rotate the cylindrical body 220. The movement of the cylindrical body 220 changes the position of the trailing edge 214 from a first position to a second position that is angularly offset from the first position.

The side view of FIG. 3 shows that the stepped profile of the boss 218 forms a lower boss portion 238 and an upper boss portion 240. The lower boss portion mates with the disc surface 232 of the round disc 230. The vane body 202 has a recess 242 with a recess surface 244. In one example, the upper boss portion 240 mates with the recess surface 244 to maintain planarity of the vane body 202 when in position, e.g., in a compressor device.

The cylindrical sleeve 234 can extend directly from the bottom of the round disc 230 or, as shown in FIG. 3, can be spaced apart to accommodate for various assembly dimensions and/or tolerance stackup. Examples of the sleeve 234 can provide an elongated bearing surface that works in cooperation with a bore into which the cylindrical sleeve is inserted to facilitate rotational motion of the diffuser vane 200. In one example, the cylindrical sleeve 234 can insert into a separately configured bearing element (e.g., a bearing sleeve or like element).

As best shown in FIG. 4, the aerodynamic shape of the vane body 202 has a suction side surface 246 and a pressure side surface 248 identified relative to the orientation and angle of attack of the leading edge 212 relative to the flow F of the working fluid. At the leading edge 212, the vane body 202 converges to a tip 250 that can be round and/or can have a curvilinear outer surface. The rotation axis 216 is proximate the center of the tip 250 and, in one example, the rotation axis 216 is coaxial with the center axis of the tip 250.

The boss 218 extends along a camber line C, which bisects the vane body 202 The camber line C defines the locus of points midway between the suction side surface 246 and the pressure side surface 248. The boss 218 has a proximal end 252 near the tip 250 and a distal end 254 spaced apart from the proximal end 252 a distance D along the camber line C. The boss 218 also extends on either side of the camber line C, wherein the stepped profile forms a plurality of peripheral edges (e.g., an inner peripheral edge 256, an intermediary peripheral edge 258, and an outer peripheral edge 260). The peripheral edges 256, 258, 260 define the outer boundary of the lower boss portion 238 and the upper boss portion 240. In one embodiment, the boss 218 has contoured and/or aerodynamic surface to minimize flow disturbances if, for example, a portion of the boss 218 resides in the flow of the working fluid.

The dimensions of the boss 218 can help to tune construction of the diffuser vane 200 to prevent unwanted vibration. For example, the width of the boss 218, e.g., between the peripheral edges 256, 258, 260, can vary to accommodate variations in flow parameters (e.g., velocity, density, volume, etc.) that can cause stimulating frequencies that vibrate the diffuse vane 200. In one example, the width is measured between the peripheral edges 256, 258, 260 on either side of the vane body 202. In one example, the peripheral edges 256, 258, 260 are configured so that at least a portion of the peripheral edges 256, 258, and 260 are spaced apart on opposite sides of the camber line C by equal amounts. Likewise, modifications in the length of the boss 218, e.g., the distance D from the proximal end 252 to the distal end 254 and the distance from the rotation axis 216 to each of the proximal end 252 and the distal end 254, may provide better support and/or protect against vibration under certain conditions. In one example, the distance D is 35% or less of a chord length for the vane body 202 that is the straightline distance as measured between the leading edge to the trailing edge.

Examples of the diffuser vane 200 can be constructed of various metals and composites that meet the operational criteria, e.g., of a type of compressor device. As set forth above, the diffuser vane 200 can comprise one or more separate pieces, which collectively form the form factor and structure of the diffuser vane 200 when assembled together. Fasteners (e.g., screws, bolts, etc.) and securing materials (e.g., adhesives and welds) can couple the parts together in a manner that withstands the flow of the working fluid. In one implementation, the stepped profile may comprise a plurality of differently configured material blanks of the same and/or varying properties (e.g., material) and dimensions (e.g., material thickness). These material blanks can stack on top of one another to construct the profile (e.g., stepped profile) of the boss 218. Examples of the material blanks can be interchangeable to tune the modal frequency of the diffuser vane on site and/or during final characterization and optimization of compressor device.

FIG. 5 shows another exemplary embodiment of a diffuser vane 300 in position as part of a diffuser assembly 362, which itself finds use in a compressor device. The diffuser assembly 362 includes a inlet cover 364 with an array of bores 366 that are circumferentially spaced about the center of the inlet cover 364. In the present example of FIG. 5, the bores include a through bore that penetrates the thickness of the inlet cover 364 and a counter bore, which has a diameter to receive the round disc 330. The counter bore also forms a surface at a depth to position the structure of the diffuser vane 300 in the flow of the working fluid.

FIG. 6 shows a front, perspective view of the diffuser assembly 362. As shown in FIG. 6, the inlet cover 364 has a recessed front face to receive an annular ring member 368 therein. A plurality of bearing elements 370 mount to the inlet cover 364. The bearing elements 370 engage the inner radial part of the annular ring member 368. The diffuser assembly 362 also includes a force coupler 372 with a linkage member 374 that secures to the annular ring member 368 at a first end. The linkage member 374 has a second end that secures to a force coupler 376, which mates with a portion of the diffuser vane, e.g., the shaft 336 In one example, the diffuser assembly 362 further includes an actuator assembly with a first yolk member 378 and a second yolk member 380 that couple an actuator 382 with, respectively, the inlet cover 364 and the inner ring member 368. This configuration of elements secures the actuator 382 in place, e.g., on the inlet cover 364 (which is itself generally stationary within a compressor device). Examples of the actuator 382 include pneumatic cylinders, lead screws, devices, and the like. The type of device for the actuator 382 may depend on the necessary level of accuracy that is required to position the trailing edge to achieve certain operation parameters for a compressor device.

During operation, movement of the actuator 382 can cause the annular ring member 368 to rotate in either a clockwise direction or a counterclockwise direction. Rotation of the annular ring member 368 causes the linkage member 374 to move, which in turn rotates the force coupler 376. The shaft 336 rotates in response to movement of the force coupler 376 to change the position of the trailing edge of the vane body between a first position and a second position that is angularly offset from the first position.

FIG. 7 shows the diffuser assembly 362 in exploded form. In one example, the diffuser assembly 362 further includes one or more sleeve members 384. Examples of the sleeve members 384 can slide onto one or more of the cylindrical sleeve 334 and/or the shaft 336 of the diffuser vane 300. In one example, the sleeve members 384 can comprise a bearing or bearing material that prevents contact between the interior surfaces of the bore 366 and the outer surfaces of the diffuser vane 300. The sleeve members 384 provide a low friction surface about which the shaft 336 (and other part of the diffuser vane) can rotate.

FIG. 8 depicts an example of a diffuser vane 400 as part of a diffuser assembly 462 in a compressor device 486. In the example of FIG. 8, the diffuser assembly 462 has a plurality of the diffuser vanes 400 including, in one example, one that aligns with each of the bores 466 found on the inlet cover 464. The compressor device 486 also includes a volute 488, shown in phantom lines to illustrate the position of the diffuser vanes 400 therein. The volute 488 has an outlet 490 from which the working fluid exits the compressor device 486. In one example, the compressor device 486 also includes a drive unit 492, e.g., a electric motor.

In one embodiment, the volute 488 surrounds the diffuser vanes 400, forming an interior diffuser cavity through which the working fluid can flow past the diffuser vanes and onto the outlet 490. While construction of the diffuser assembly 462 indicates the diffuser vanes 400 insertably engage with the inlet cover 464, this disclosure contemplates configurations, e.g., of the diffuser assembly 462, in which the diffuser vanes 400 couple with and/or secure to structure of the volute 488, the compressor device 486, as well as with plates, walls, tubing, and other members that can support the diffuser vanes 400 and allow movement of the trailing edge as disclosed herein.

FIG. 9 depicts a front view of the compressor device 486. The compressor device 486 has an inlet 494 with an impeller 496. The inlet cover 464 is disposed circumferentially about the impeller 496. In one embodiment, and as shown in FIG. 10, the compressor device 486 also incorporates a front cover 498, which fits over the front face of the compressor device 486 to limit exposure of the diffuser assembly 462. Examples of the compressor device 486 find use in a variety of settings and industries including automotive industries, electronics industries, aerospace industries, oil and gas industries, power generation industries, petrochemical industries, and the like. During operation of the compressor device 486, the drive unit 492 rotates the impeller 496 to draw a working fluid (e.g., air) through the inlet 494. The impeller 496 compresses the working fluid. The compressed working fluid flows into the volute 488, through the diffuser assembly 462, and out of the outlet 490.

In one implementation, operation of the drive unit 492 turns the impeller 496 to draw the working fluid through the inlet 494. The impeller 496 pressurizes the working fluid. The pressurized working fluid passes through the diffuser assembly and, in particular, through channels between adjacent diffuser vanes. At a high level, the diffuser assembly slows the velocity of the working fluid downstream of the impeller 496. The diffuser assembly discharges into the volute 488, which delivers the working fluid, e.g., to a downstream pipe that couples with the outlet 490.

Generally examples of the compressor device 486 undergo extensive performance testing and tuning to optimize performance for a given implementation. Tuning often entails modifying operation, e.g., of the drive unit 492, to adjust the speed of the impeller 496, which changes flow parameters (e.g., pressure, flow rate, etc.) of the working fluid that exits the outlet 490. Performance of the compressor device 486 will also change in response to the orientation of the diffuser vanes. In one example, tuning involves adjusting the orientation of the diffuser vanes, which can modify, among other things, the pressure of the working fluid at the outlet 490. Collectively, to optimize the flow parameters, tuning will likely make incremental and/or iterative changes to several operating settings (e.g., speed of drive unit 492, orientation of diffuser vanes, etc.) of the compressor device 486 to achieve combinations of operating parameters that cause the compressor device 486 to operate efficiently to achieve desired flow parameters.

Examples of the diffuser vanes can be constructed of various materials and combinations, compositions, and derivations thereof. These materials include metals (e.g., steel, stainless steel, aluminum), highstrength plastics, and like composites. Material selection may depend on the type and composition of the working fluid. For example, working fluids with caustic properties may require that the diffuser vanes comprise relatively inert materials and/or materials that are chemically inactive with respect to the working fluid.

Geometry for the diffuser vanes can be determined as part of the design, build, and fitting of the compressor device 486 for the application. The geometry can include airfoil shapes (e.g., the shape shown in FIGS. 2, 3, and 4) for the vane body, examples of which take the form of wings and blades and/or other forms that can generate lift. In one embodiment, the diffuser vanes can mount, e.g., to one of the wall members, using fasteners and fastening techniques that permit rotation of the diffuser vanes about the leading edge.

In view of the foregoing discussion, embodiments of the diffuser vane and diffuser assembly contemplated herein improve performance of compressors and related devices. In one example, and as set forth above, the trailing edge of the diffuser vanes rotates about the leading edge, which effectively reduces flow separation of the working fluid from the surfaces of diffuser vanes. This feature improves performance of the compressor over a larger flow range because the leading edge remains oriented with the flow direction of the working fluid.

As used herein, an element or function recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or functions, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the claimed invention should not be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A diffuser vane for use in a diffuser assembly downstream of an impeller in a compressor device, comprising: a vane body having a top, a bottom, a leading edge and a trailing edge, the leading edge having a rotation axis; a support element coupled to the bottom of the vane body proximate the leading edge, the support element forming a boss with a peripheral edge disposed on either side of the vane body; and an armature coupled to the support element, the armature having a cylindrical body terminating in a shaft.
 2. The diffuser vane of claim 1, wherein the boss has a stepped profile with an upper boss portion and a lower boss portion that couple, respectively, to the vane body and the cylindrical body, and wherein the upper boss portion is narrower than the lower boss portion.
 3. The diffuser vane of claim 1, wherein the peripheral edge of the boss is spaced apart from a camber line of the vane body by equal amounts.
 4. The diffuser vane of claim 1, wherein the cylindrical body has an axis aligned with the rotation axis.
 5. The diffuser vane of claim 1, wherein the cylindrical body comprises a round disc with a disc surface on which the boss is disposed
 6. The diffuser vane of claim 1, wherein the vane body comprises an airfoil.
 7. The diffuser vane of claim 6, wherein the rotation axis is coaxial with a center axis of a tip at the leading edge of the airfoil.
 8. The diffuser vane of claim 1, wherein the boss has a proximal end near the leading edge and a distal end that is remote from the cylindrical body.
 9. The diffuser vane of claim 8, wherein the distal end is spaced apart from the proximal end a distance that is 35% or less of a chord length for the vane body that measures the straightline distance from the leading edge to the trailing edge.
 10. The diffuser vane of claim 1, wherein the vane body has a recess in the bottom to receive the boss.
 11. A diffuser assembly for use downstream of an impeller in a compressor device, comprising: a inlet cover having a bore; a diffuser vane disposed in the bore, the diffuser vane comprising a vane body having a leading edge and a trailing edge and an armature coupled to the vane body, the armature extending through the inlet cover; and a force coupler coupled to the armature, wherein the diffuser vane secures to the armature to permit rotation of the trailing edge about the leading edge between a first position and a second position that is angularly offset from the first position.
 12. The diffuser assembly of claim 11, further comprising an annular ring member disposed on a recessed front face of the inlet cover, wherein the force coupler couples to the annular ring member, and where the vane body moves between the first position and the second position in response to rotation of the annular ring member.
 13. The diffuser assembly of claim 11, wherein the bore comprises a through bore and a counter bore that is larger than the through bore, wherein the counter bore forms a surface that mates with a round disc of the armature.
 14. The diffuser assembly of claim 11, wherein the diffuser vane comprises a support element that couples with the vane body, and wherein the support element forms a boss disposed on the armature with a peripheral edge disposed on either side of the vane body.
 15. The diffuser assembly of claim 14, wherein the boss is wider than the vane body.
 16. A compressor, comprising: an impeller; a inlet cover disposed circumferentially about the impeller, the inlet cover comprising a bore extending from a diffuser cavity through the inlet cover; a diffuser vane disposed in the diffuser cavity downstream of the impeller, the diffuser vane comprising a vane body having a leading edge and a trailing edge, a support element disposed on the vane body, and a cylindrical body coupled to support element, the cylindrical body having an axis that aligns with a rotation axis proximate the trailing edge and about which the trailing edge rotates between a first position and a second position that is angularly offset from the first position.
 17. The compressor of claim 16, wherein the support element comprises a boss that has a proximal end near the leading edge and a distal end that is remote from the cylindrical body.
 18. The compressor of claim 17, wherein the distal end is spaced apart form the proximal end a distance that is 35% or less of a chord length for the vane body that is measured from the leading edge to the trailing edge.
 19. The compressor vane of claim 16, wherein the cylindrical body comprises a round disc with a disc surface that mates with a surface of a counter bore axially aligned with the bore on the inlet cover.
 20. The compressor vane of claim 16, further comprising a volute that forms a portion of the diffuser cavity. 